Problematic internal links in InDesign CS6 to pdf

Hi all, 

I have two problems with internal links in an Indesign CS6 document. 

1. The internal links worked fine in the original .indd file (i.e. clicking on a word leads to the correct page in the same document(Anchor)). 

However, when exporting to a .pdf file, the internal links don't work, and clicking on it does nothing. 

There seems to be no logic to it - some links work, others don't. The info is correct in the Links window.

2. Some of those internal links are suddenly referred to an external destination (website , which is wrong destination in this case) despite no changes made to these particular pages.

 Did anyone encounter this problem?